We all know that Morrowind was released in various languages editions, right. Now, is there any possibility to convert non-english (no matter, italian, polish or french) modification into working one on english version of Morrowind?

Simply, yes.

You can open and edit mods with third-party tools which don't worry much about language. It's also reasonably trivial to define a set of rules (search and replace) to match things up between translations.

In practice, you need to do quite a bit of work to make sure the various IDs and such line up, or the game may end up crashing. It may be tedious, as there are no/few references available, so you would have to use the master files from both languages.

So, after your respond, may I suppose that there is none of any language converter, yes?